An Investigation into the Activity of the Neyshabour Fault, Khorasane Province, Iran

Neyshabour (approximately 200,000 pop.) lies on the southern margin of the Binalud mountains in NE Iran. The city has been destroyed four times by major historical earthquakes (in 1209, 1270, 1389 and 1405 A.D.).Three large faults occur in the region. The Binalud and North Neyshabur faults lie at the foot of the Binalud range north of Neyshabour. The Neyshabour fault lies within the valley west of Neyshabour. The Neyshabour fault, which lies 10 km south of the North Neyshabur fault, is 50 km long thrust. At each end of the Neyshabour fault two young, 10 km-long, thrust segments occur. It is close to Neyshabour city; and is a probable source of the 1209 and 1405 earthquakes. It poses a substantial seismic risk to the city because of the potential for future activity. Slip rate is one of the important parameters for seismic hazard assessment which was determined using SRTM for offset measurement and OSL for age calculation. Luminescence was measured through 7 mm Hoya U-340 filters in a Risø (Model TL/OSL-DA-15) automated TL/OSL system. The equivalent dose (De) was obtained using the conventional quartz single aliquot regeneration method (Murray and Wintle, 2000). Twelve aliquots have been processed for the sample, of which only the aliquots were accepted that satisfied the SAR restrictions. De was estimated using analyst program. Age was calculated using a weighted mean De for the sample. The Dose rate was obtained using uranium, thorium and potassium concentrations, which were measured by Micro Nomand portable gamma spectrometer in field. The results are presented in Table 1. Dividing the displacement by the minimum and the maximum ages provided the slip rate to be 0.1-0.2mm/yr.